Electrical measuring instrument.



VV, E. BEEDE.

ELECTRICAL MEASURING INSTRUMENT.

APPLICATION man ram/22,1915.

QTQ? Patented Mar. 2T, 191?.

WALTER E. B'EEDE, 0F NEVI YORK, 13T.

ELECTRICAL MEASRNG INSTRUMENT.

Application led May 22 To oZZ whom z may concern Be it .known that l, lYAnTne E. Bumm, a. citizen of the United States, residing at borough ot lllanhattan, city of New York, in the county, ci' New York and State of 7Sew York, have invented certain new and useful improvements in Electrical Measuring instruments, of which the 'following is a specification, reference being hadtherein to the accompanying drawings, forming part thereot.

My invention relates to electrical measur- `ing instruments of that kind which are adapted to give readings or current indications at opposite sides of a aero point, and relates more particularly to such instruments in which a permanent field magnet is employed for biasing or giving direction to a pivoted magnetic armature which is adapted to be displaced or deflected one way or the other relative to the zero point, according to the direction ot' current through an adjacent electric coil.

ln instruments such as referred to above great ditiiculty has been encountered in efr'ort-s to so construct them that they will give similar or corresponding current indications at each side of the zero point,rso

that accurate current indicatmns W1ll be i given at both sides of the zero point of a `synnnetrically calibrated scale over which same current strength and thereby vnecessarily giving an inaccurate indication at either one or bothsides ot the zero indication on the calibrated scale. Commonly hertofore electrical measuring instruments have only been provided with means for adjusting the movements of the indicating pointer relative to the scale as a wholerand while such means anstver the purpose for a'calib'rated scale reading from Zero in one direction only, it is evident that they would not suttice in the case of double scale having a middle zero point, as correction could be made for onev side oi the scale only. Here* i tot'ore in some instances with expensive instruments, each instrument has been pro Specification of Letters'Patent.

lpatented tirar. 2t', i917?.

, 1915'. serial ne, 29,843.

vided with a dial which rwas especially calibrated 1n accordance with tests of that particular instrument.

A present extensive use of instruments of the type mentioned, that is, which give current indications at one oi' the other sideot a zero point according to the direction of the current, is in electric lighting or lightingand engine starting equipments of motor vehicles, where they are employed to indicate the strength of the current flowing to or from a storage battery, and for this purpose the double calibrated dial, in addition to its calibrations, is commonly also marked with words, such, for example, as Charge and l)iscliarge, to indicate Whether the storage battery is receiving a charge or the cur.- rent is being used therefrom. ln these instruments accuracy of indication at, both sides of the zero point is important, and although accuracy was 4not commonly obtained, the expense of manufacture ot the instrument was considerably increased by eff. orts'to obtain as close an approximation to accuracy as Was possible. i

rlhe principal object of my invention is to produce an instrumentl which can be adjusted to overcome or compensate for slight inaccuracies of manufacture so as tofobtain correct indications at both sides of the zero point,- on apreviously calibrated scale. Other objects of my invention are reliability, simplicity of construction, inexpensiveness of manufacture, and other objects and advantages which will hereinafter appear.

`My invention broadly includes means for producing a differential effect in or for distorting the magnetic field to vary the current indications at opposite sides of the zero point so that correct current indications will be given at both sides of the zero point on the calibrated scale; such, for example, as a Weak pivoted polar extension. fromeach of the opposed poles of a permanent field magnet. My invention more particularly includes features o'f construction and combinations of'parts' as will appearrom the tolloiving description.

l shall noiv describe the electrical measuring instrument embodying my invention illustrated in the accompanyingdrawings and shall tli rea-iter point out my inven-- embodying my invention.'

Fi". 2" is a similar View with the front part of the) casing and dial removed.

Fig. 3 isa central vertical section on a plane indicated by the lines 3-3 otFigs. l and 2 as Viewed from the right and of Fig. 4 as viewed from the left.

' F ig. t is a rear View of the instrument with the base plate removed.

Figf is a horizontal section on a plane indicated by the lines 5-5 of Figs. 1, 2 and 3 as viewed from above.

In the embodiment of my invention illustrated in the accompanying drawings, pivotally shiftably pa 'amagnetic adjusting members l are lprovided and these members comprise thin strips of magnetizable material such as soft iron which at one end are A adjustably'pivoted by means ot magnetizable screws 2 t0 a non-magnetic back plate 3 of the instrument. The magnetizable pivot screws 2 project inward through the back-plate 3 tovard and preferably, as shown inthe drawings, into Contact with the spaced opposed poles ot a. permanent circular or ring-shaped field magnet a, shown as made up of two plates or laminfe. The back plate 3 is shown as having indentations forming inward projections or protuberances upon which the field magnet 4 1sv supported in spaced relation to the flat main portion of the back plate 3 by means of bolts 5, the enlarged cylindrical heads et which form. spacers at the front ot the magnet 4 and receive screws G which support a non-magnetic dial 7 in spaced relation to the magnet 4. The dial 7 is shown as provided ivith a symmetrically calibrated scale reading in both directions trom a middle zero point, that is to say, both parts of the scaleare alike excepting that one part reads from the middle to the lett and the other part reads from the middle to the right, thepart of the seal? at the lett ot the zero point being marked (lharge and the part of the scale at the right ot the zero point being marked Discharge A paramagnetic pivoted armature 8, show-n as of rounded elongated or oval shapeI` is located in the magnetic field of the. magnet 1l between the opposed poles thereof. The aruulture S is carried by an arbor 9 the ends ot which arej'iivotally supported by a sheet metal bracket 10 tixed on the back plate The arbor 9 also carries a non-magnetic counter-Weight 11 and a non-. magnetic pointer or indicatingr hand 12 which. projects through a slot to the i'ront ot' they dial 7 tor cooperation with the ealibrated saale. thereon. A coil 13 is shown as located within the. ring formed by the iield magnet Je and arranged to produce a magnetic field at right-angles to that producedl by the field magnet -t between its poles. For strengthening its field the coil 13 has a non-magnetized paramagnetic core 1li which, at the end adjacent to the pirated armature 8, is provided ,rith a thin transversely projecting curve-f;l head '15 which partly bridges the space :.ietu'een the peice of the magnet Lt at the side of the pivoted armature S and advantageousiy distributes the magnetic field produced by the eoil At its other end from the magnetizable head or pole piece 15, the magnetizable core il is supported on the back plate 3 by an la shaped bracket 16. The turns of the coii 13 are insulated from each other by an insulating covering oi? enamel, for example., and the coil i3 is additionally insulated trom its core ii. pole piece 15 and support ingl bracket 16 by means uit an insulating tube i7, which may be ot' paper or cei leid, and insulating and plates i8, what.

may be of vulcanized liber. The 'ree ends of the coil 1.3 are shoivnas soldered to eenvduetive standards 19 which are held in piace on the back plate 3 by and are in eleetri cal connection ywith bolts 2O which form conductive attaching stems for the instr ment and also serve as binding posts for the circuit ivires, the conductive standards i9 and the attaehing stems` Q0 being insulated from the conductive baci: plate 3 as shown in. the drawings. di thin nou-magnetic metal easing Qi is shown secured by means of small bolts. to `the outer edge or margin of the bark plate El and the Ieasing part 91 is closed at the front by a crystal glass QQ. The instrument has a base plate 23 of suitable insulating material, such as hard rubber which is held in place by eel means ot` insulating sleeves 2l on theattaehl ing stems Qi).

in the operation ot the instrument, the current indications ot the pointer 12 on the calibrated dial 7 are intiueneed by the shape and relative,positions ot' the fieldv magnet. li, maguetizable armature S and magnetizable pole piece l5; The pivotally shii'table paramagnetie adjusting members l constitute waak polar extensions 'from the opposed poles of ther permanent tield magnet i. ily slightly loosening the magnetizable pivot screws 2 the adjusting members i may be shifted to dill'erent pivotal or angular positions, each indejmidently ot' the other. These pivotallyanovable polar extensions may be employed to adjust `the strength ot' the available magnetic field as a Vwhole and also may be employed to produce a distortion or diilerential eli'eet in the magnetie field. liyi pivotally shifting both'ot the members i proportionately or eoriespondingly, the strength ot all partsot' the magnetic field will be equally aii'eete'd and the movements ot the pointer 'l2 u'ill be similarly atl'eeted throughdut the length ot the sealc. llowever. iie these two members lla"- adjnsted to ditl'erent. angular positions for drawings, they will then act with a distort` ing or differential effect upon the-magnetic field of the permanent magnet el, as such field .may be influenced by the coil 3 andits magnetic core 14 and pole piece 15, and the movements of the pointer 12 will be correspondingly differentially affected so that for the same strength of current the pointer 12 willA move farther over one of theparts of the calibratedkscale and not so far over the other part thereof as it would without such differential adjustment, and thereby inaccuracies of manufacture can be compensa-ted for and correct current indications obtained at both 'sides of the zerb point on the v"calibrated dial 7.. For example, in the posi tions of the adjusting members l illustrated in the drawings, it has been found that, for a given strength of current, the pointer 12 will not move so far to the left as it would without these members l, and that it will move correspondingly farther to the right.

It has been found that a' range of adjust.

ment to' the extent of aboutfonethird of the scale can be effected and that this is ample for* all practical purposes. In making this differential adjustment of the instrument the position of the pointer i2 relatively to the zero point will be slightly affected, but this displacement of the pointer can be readily corrected by slightly bending the pointer 12 so it will stand at the zero indication in the no `current condition of the circuit in which the instrument is included. All of the dials 7 are calibrated alike and each instrument before it leaves the factory is tested and the magnetic members 1 adjusted .to positions which will cause the pointer- 12 to indicate correctly at both sides of the zero point.

In the drawings the pivotally shiftable polar extensions 1 are shown as adjusted to different angular positions in which both are above or inward from the axis of the pivoted magnetic armature 8, but it should be understood that similar though lesser results would follow by correspondingly shiftingboth of these members l downward or outward from the axis of the armature 8. Also one of these members can be swung upward and the other downward and a'differential or distorting effect be produced. Furthen more,if desired, both of the polar extensions l can be turned toward and into contact with each other, thereby producing a weak closed magnetic shunt equally affecting the whole field; or both of the membcrs'l can be turned back alongside` of the poles of the magnet 4, and in this position their effect would be substantially nulliiied and the field would retain its greatest strength.

It is obvious that various modifications may be made in the construction shown in the drawingsy and ,above particularly described within the principle and scope of my invention.

headset E claim: 1 l. An electrical measuring instrument comprising a permanent magnet having opposed poles, a pivoted magnetic indicating armature in the field of the magnet and pivptally"movable to give current indications at opposite sides of a zeropoint, an

Ations at opposite sides of' a zero point7 an electric coilfor deflecting the armature on its pivot in one direction or the other according to the direction4 of current through the coil, a magnetic core for the coil having a head extended transversely between the poles of the permanent magnet, and a pivotally shiftable polar extension from one of the. magnet poles for influencing the armature to give like current indications at opposite sides of the zero point.

3. An electrical 'nneasuring instrument comprising a permanent magnet having opposedpoles, a pivoted magnetic indicating armature in the field of the magnet and pi'votally movable to vgive current indica- 'tions at oiiosite sides of a zero oint an electric coil for defiecting the armatureon its pivot in one direction or the other according to the direction of current through the coil, a magnetic core for the coil having a transversely extended head Iforming a pole piece partly bridging the space between the magnet poles at the side of the armature, and a pivotally shiftable polar extension from each of the magnet poles for distorting the magnetic field so'as to influence the armature to give correct current indications at both sides of the zero point.

4. An electrical measuring instrument comprising a permanent magnet having opposed poles,A a. pivoted magnetic indicating armature in the field of the magnet and pivotally movable to give current indications at opposite sides ofa zero point, an electric coil for deflecting the armature on its pivot in one direction or the other ac cin-ding to the direction of current through the coil, a magnetic core for the coil having a transversely extended head forming a pole piece partly bridging the space between the magnet poles at thev side of the armature, and a pair of independently pivotally shiftable magnetic adjusting niembers .in the magnetic field for adjusting the instrument to give correct current indications at both sides of the zero point.

An eleetrieaimeasuring 'instrument having, in combination, a permanent field magnet having opposed poles,A a non-mag netie supporting plate for such magnet, and a pair of' pivotaliy shiftable pole pieces forming polar extensions pivoted to the nonmagnetie magnet supporting plate. i

(3. An electrical measuring instrument having, in combination, a permanent eid magnet having opposed poles, a non-magnetic supporting plate for such magnet, a

pair of pivetaliy shif'tabie pole pieces infin ing polar extensions plvoted te the nenmagnet-ie pivot screws for the pole pieces passing through the non-magnetic suppe'rt ing piate intev close magnetic rei-ation the poles of the magnet.

In testimony whereof have affixed injvA signature in presence of two Witnesses.

WULTER E, BEEDE. TVitnesses WVM. ASHLEY KELLY, JOSEPH F. DUNN. 

